NoSQL databases, in contrast with relational databases (such as older versions of MySQL and PostgreSQL), shine when the amount of data becomes too big, and also when we don't need the Features of relational databases (such as triggers or stored procedures).

Before we continue, let's list out the advantages of NoSQL systems:

• Scale horizontally; to get more performance, just add more machines
• We don't need to know in advance the relations between tables
• Allow changing tables structure while the whole thing is working
• Faster (no complex relational database mechanism)
• Data is normally saved on distributed filesystems, so, for example, storing images in NoSQL databases is fine